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Title:
DRIER CRUSHER INSTALLATION
Document Type and Number:
WIPO Patent Application WO/2009/092645
Kind Code:
A1
Abstract:
A method for producing cement clinker from raw material in a cement plant, by which method hot gases from a kiln system (3), through an inlet duct (4), which is connecting the kiln system (3) to a drier crusher (1 ), are directed into the drier crusher (1 ) to which also raw material, via a raw material inlet (5), is fed in order to be crushed and dried for subsequently, in suspended form, to be carried to a classifier (2) via an outlet duct (6), which is connecting the drier crusher (1 ) to the classifier (2). The method is peculiar in that at least some of the hot gases in the inlet duct (4), via a bypass duct (7) connecting the inlet duct (4) to the outlet duct (6), are bypassed the drier crusher (1 ) and directed into the outlet duct (6) at a location between the classifier (2) and the drier crusher (1 ). Hereby it is obtained that the raw material is further dried by the bypassed gases while being carried to the classifier. In this way the volume of hot gases used for drying can be increased, i.e. the drying capacity of the system can be increased without causing an increase in the pressure loss across the drier crusher.

Inventors:
GRYDGAARD PALLE ERIK (DK)
EIMERT RICHARD (DK)
JENSEN STIG (DK)
Application Number:
PCT/EP2009/050309
Publication Date:
July 30, 2009
Filing Date:
January 13, 2009
Export Citation:
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Assignee:
SMIDTH AS F L (DK)
GRYDGAARD PALLE ERIK (DK)
EIMERT RICHARD (DK)
JENSEN STIG (DK)
International Classes:
F27B7/20; C04B7/43; C04B7/44; F27D17/00
Domestic Patent References:
WO2007099415A12007-09-07
Attorney, Agent or Firm:
HYNELL PATENTTJĂ„NST AB (Uddeholm, SE)
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Claims:
Claims

1. A method for producing cement clinker from raw material in a cement plant by which method hot gases from a kiln system (3), through an inlet duct (4), which is connecting the kiln system (3) to a drier crusher (1 ), are directed into the drier crusher (1 ) to which also raw material, via a raw material inlet (5), is fed in order to be crushed and dried for subsequently, in suspended form, to be carried to a classifier (2) via an outlet duct (6), which is connecting the drier crusher (1 ) to the classifier (2) characterized in that at least some of the hot gases in the inlet duct (4), via a bypass duct (7) connecting the inlet duct (4) to the outlet duct (6), are bypassed the drier crusher (1 ) and directed into the outlet duct (6) at a location between the classifier (2) and the drier crusher (1 ).

2. A method according to claim 1 characterized in that the classifier (2) classifies the raw material into at least a fine and a coarse material fraction, where the coarse fraction is returned to the drier crusher (1 ).

3. A plant for manufacturing cement clinker from raw material comprising a drier crusher (1 ) which, via an inlet duct (4), is connected to a kiln system (3) from where hot gases through the inlet duct (4) are directed into the drier crusher (1 ) wherein raw material, via a raw material inlet (5), also is fed to undergoing crushing and drying prior to, in suspended form, being directed to a classifier (2) through an outlet duct (6) which is connecting the drier crusher (1 ) to the classifier (2) characterized in that it comprises a bypass duct (7) which is connecting the inlet duct (4) to the outlet duct (6) at a location between the classifier (2) and the drier crusher (1 ).

4. A plant according to claim 3 characterized in that the gas flow through the bypass duct (7) is controlled by regulating means (13).

5. A plant according to claim 3 characterized in that the drier crusher (1 ) is a hammer mill drier.

Description:

DRIER CRUSHER INSTALLATION

The present invention relates to a method for producing cement clinker from raw material in a cement plant by which method hot gases from a kiln system, through an inlet duct, which is connecting the kiln system to a drier crusher, are directed into the drier crusher to which also raw material, via a raw material inlet, is fed in order to be crushed and dried for subsequently, in suspended form, to be carried to a classifier via an outlet duct, which is connecting the drier crusher to the classifier. The invention also relates to a plant for carrying out the invention.

A plant as well as a method of the aforementioned kind is well-known in the cement manufacturing industry. In fact, the plant described is used in many cement plants around the world where the available cement raw material has a high content of water. Hot gases from a kiln system and raw material, such as chalk, marl and clay, are fed to a drier crusher where the raw material is crushed and dried and subsequently in suspended form carried through a classifier and further to a cyclone in which the raw material is separated from the gases. The separated raw material is introduced into a preheater in the kiln system whereas the gases are carried to a filter for final cleaning. In this kind of plant all the hot gases from the preheater are normally transported through the drier crusher. The higher velocity of the gases through the drier crusher the higher the pressure loss across the drier crusher will be. Therefore the volume of hot gases, which is transported through the drier crusher, is linked to the maximum acceptable gas velocity through the crusher, i.e. the maximum acceptable pressure loss across the drier crusher. Therefore it is not profitable to increase the volume of hot gasses through the drier crusher system in order to increase the drying capacity when the gas velocity through the crusher has reached the maximum acceptable velocity.

It is the object of the present invention to provide a method by means of which the disadvantage of the aforementioned known method is significantly reduced.

This is obtained according to the invention by a method of the kind mentioned in the introduction and being characterized in that at least some of the hot gases in the inlet duct, via a bypass duct connecting the inlet duct to the outlet duct, are bypassed the drier crusher and directed into the outlet duct at a location between the classifier and the drier crusher.

By bypassing some of the hot exhaust gases the volume of hot gases used for drying can be increased, i.e. the drying capacity of the system can be increased without causing an increase in the pressure loss across the drier crusher. This increased drying capacity is due to the fact that the raw material is further dried by the bypassed gases while being carried to the classifier. Furthermore, to a certain extent, it will be possible both to increase the raw material feed, as a result of the increased drying capacity, and to reduce the pressure loss across the drier crusher at the same time. This can be achieved by directing less gas through the drier crusher and more gas through the bypass duct. Hereby the total energy used for the production of clinker is reduced. The savings are estimated to not less than 1 kWh/t clinker.

It is preferred that the gas flow through the bypass duct is controlled by regulating means which could be a valve or any other kind of suitable means which are able of regulating a gas flow through a duct. In this way it is possible to control the gas flow through the drier crusher in order to maintain the pressure loss across the drier crusher at a predetermined level.

It is preferred that the classifier, which classifies the raw material into more material fractions, classifies the raw material into at least a fine and a coarse fraction, where the coarse fraction is returned to the drier crusher. Furthermore the classifier may also classify a very coarse fraction which could be directed to a separate grinding installation.

In a preferred embodiment the drier crusher is a hammer mill drier, which is particular suitable for processing softer cement raw materials with a high content of water.

The invention will now be explained in further details with reference to the drawing, being diagrammatical, and where the figure shows a plant according to the invention.

The shown kiln system 3 in the figure, which is not a part of the present invention, is a traditional kiln system 3 comprising a preheater 8, a calciner 9, a rotary kiln 10 and a clinker cooler 11 in which raw materials in known manner are preheated, calcined, burned into cement clinker and cooled. In addition to the above-mentioned, the plant comprises a drier crusher 1 which, via an inlet duct 4, is connected to the preheater 8 in the kiln system 3. The hot gases from the preheater 8 are directed through the inlet duct 4 into the drier crusher 1 wherein raw material, via a raw material inlet 5, also is fed to undergoing crushing and drying prior to, in suspended form, being directed to a classifier 2 through an outlet duct 6 which is connecting the drier crusher 1 to the classifier 2. At least some of the hot gases in the inlet duct 4 are bypassed the drier crusher 1 via a bypass duct 7 which is connecting the inlet duct 4 to the outlet duct 6 at a location between the classifier 2 and the drier crusher 1. Hereby it is obtained that the raw material is further dried by the bypassed gases while being carried to the classifier 2 from the drier crusher 1. In the classifier 2 the raw material is classified into a coarse material fraction, which is returned to the drier crusher 1 for further drying and crushing, and a fine material fraction. The fine material fraction is in suspended form directed to a cyclone 14 in which the raw material is separated from the gases and directed to the preheater 8 or an intermediate storage silo whereas the gases are directed to a filter, not shown, for cleaning. The gas flow through the bypass duct 7 is controlled by a valve 13. In this way it is possible to control the gas flow through the drier crusher 1 in order to maintain the air flow across the drier crusher 1 at a predetermined level. The gas transport through the system is carried out by means of an exhaust gas fan 12 placed at a location after the drier crusher 1. No addition fan between the preheater 8 and the drier crusher 1 is needed.